Police believe a missing Canberra man could survive the freezing conditions in New York state due to his military training and the clothing worn when he was last seen almost a fortnight ago.

Forest rangers and members of the state police special operations response team are still searching for Captain Paul John McKay, an Australian Army member who police said suffered post-traumatic stress disorder.

The 31-year-old was last spotted on December 31 walking in the state's rugged north, where nearby village Saranac Lake has average January lows of minus16 degrees.

Local police said the winter clothing Captain McKay was last seen wearing was an encouraging sign.